title: Identification of TIGAR in the equilibrative nucleoside transporter 2-mediated response to fludarabine in chronic lymphocytic leukemia cells.
abstract: BACKGROUND
  The nucleoside analogue fludarabine is used in the treatment of chronic lymphocytic leukemia. It triggers p53-mediated apoptosis, although the mutational status of p53 does not fully account for heterogeneity in responsiveness to treatment. The aim of this study was to identify new genes implicated in fludarabine action as well as to determine the role of equilibrative nucleoside transporters (ENT) in the transcriptomic response triggered by this drug in chronic lymphocytic leukemia cells bearing wild type p53.
  
  
  METHODS
  We performed gene expression profiling in cells from two fludarabine-sensitive and two fludarabine-resistant cases of chronic lymphocytic leukemia treated with fludarabine either in the presence or the absence of nitrobenzylthioinosine, a hENT1-specific blocker. Twenty selected fludarabine-inducible genes were validated using Taqman low-density arrays in cells from 20 chronic lymphocytic leukemia patients with the same experimental design.
  
  
  RESULTS
  Sixteen of the twenty genes (DDB2, GADD45A, TYMS, BAX, TIGAR, FAS, TNFSF7, TNFSF9, CCNG1, CDKN1A, MDM2, SESN1, MAP4K4, PPM1D, OSBPL3 and WIG1) correlated with the ex vivo sensitivity of chronic lymphocytic leukemia cells to fludarabine, TIGAR (TP53-induced glycolysis and apoptosis regulator) being the gene that showed the strongest correlation (p<0.0001; r2= 0.6022).We observed that the transcriptomic response was weakly sensitive to the hENT1 blocker nitrobenzylthioinosine. Interestingly, we also found a correlation between hENT2 expression and induction of TIGAR after fludarabine treatment.
  
  
  CONCLUSIONS
  We demonstrate a correlation between the recently described p53-inducible apoptosis gene TIGAR and both sensitivity to fludarabine and hENT2 expression in chronic lymphocytic leukemia cells. These results, as well as the variability in fludarabine response among chronic lymphocytic leukemia patients with wild type p53, support the major role of hENT2 in the uptake of fludarabine into chronic lymphocytic leukemia cells.
authors.affiliation: Unitat d'Hematopatologia, Hospital Clínic, Institut d'Investigacions Biomèdiques August Pi i Sunyer, Universitat de Barcelona, Barcelona, Spain.
authors.forename: Mónica
authors.initials: M
authors.lastname: López-Guerra
authors.forename: Laia
authors.initials: L
authors.lastname: Trigueros-Motos
authors.forename: Miriam
authors.initials: M
authors.lastname: Molina-Arcas
authors.forename: Neus
authors.initials: N
authors.lastname: Villamor
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Casado
authors.forename: Emili
authors.initials: E
authors.lastname: Montserrat
authors.forename: Elias
authors.initials: E
authors.lastname: Campo
authors.forename: Dolors
authors.initials: D
authors.lastname: Colomer
authors.forename: Marçal
authors.initials: M
authors.lastname: Pastor-Anglada
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D051017:Apoptosis Regulatory Proteins; D033722:Equilibrative-Nucleoside Transporter 2 / Q000187:drug effects* / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000235:genetics* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D010744:Phosphoric Monoester Hydrolases; D014407:Tumor Cells, Cultured; D014740:Vidarabine / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; D033722:Equilibrative-Nucleoside Transporter 2; D047908:Intracellular Signaling Peptides and Proteins; D010744:Phosphoric Monoester Hydrolases; C512708:TIGAR protein, human; D014740:Vidarabine; C024352:fludarabine